In the United States, where beaches are still packed and football has barely made an appearance, it is probably too early to expect massive attention to be directed toward an ice hockey tournament.

But in Canada, the fourth Canada Cup that begins tonight is the focus of public attention. Hockey is Canada's sport and this tournament, most of which will be played in Canada, is the only one that attracts all the great players of the world.

While Canada and the United States must send second-level teams to the world championships and Olympics because of NHL commitments, most of the NHL's best will be at the Canada Cup to challenge the Soviet Union.

The Canadian team features Wayne Gretzky, Mark Messier, Mario Lemieux, Ray Bourque and Grant Fuhr. The United States has Pat LaFontaine, Joe Mullen, Rod Langway and John Vanbiesbrouck.

There are familiar names on the Swedish roster, too -- Bengt Gustafsson, Mats Naslund, Kent Nilsson, Hakan Loob. Finland has Jari Kurri, Petri Skriko, Esa Tikkanen.

The Soviets, eager to avenge their 1984 loss to Canada, have sent all their top players -- Sergei Makarov, Vladimir Krutov, Igor Larionov, Viacheslav Fetisov, Alexei Kasatonov. There will be even greater interest than usual in the Soviet players, because of recent indications that the U.S.S.R. is prepared at last to permit some of its stars to compete in the NHL.

Only Czechoslovakia, which has lost many quality performers to the NHL through defection, is an unknown quantity as the six-team tournament begins tonight with Team USA playing Finland in Hartford, Conn., and Team Canada playing Czechoslovakia in Calgary, Alberta.

The Czechs were horrible in the 1984 Canada Cup, failing to win a game. However, seven months later they won the world championship.

Canada has won this tournament twice. The first championship came in 1976, the second in 1984, when it defeated the Soviet Union in a classic overtime semifinal. But Canadians have not forgotten the other Canada Cup, in 1981, when the Soviets routed the hosts, 8-1, in an embarrassing final.

The tournament format involves a round robin among the six entries. One-game semifinals then send first-place team against fourth-place team and second-place against third, with the winners playing a best-of-three final.

As usual, Canada and the Soviet Union are the favorites. They split two pre-tournament exhibition games and their round-robin matchup has been scheduled for the final night of first-round play, Sept. 6.

Games have been scheduled for five Canadian cities -- Calgary, Ottawa, Montreal, Hamilton, Ont., and Halifax, Nova Scotia -- and one in the United States -- Hartford, the site of two contests involving Team USA.

The United States lost all four of its pre-tournament exhibition games against Canada, the last by 11-2. The Americans must turn things around quickly to gain the semifinals. The Finns are another fringe team and tonight's loser faces an uphill battle.

Sweden faces the Soviets Saturday in Calgary. The Swedes know that a little luck can go a long way. They edged the unbeaten Soviets on goal differential to win the world championships last May in Vienna.

"We were very lucky, when we had a tie against them," said Swedish Coach Tommy Sandlin. "I think the Russian team is the best, but in some games you can be lucky."

The Washington Capitals will be represented by seven players, spread over three teams.

Right wing Mike Gartner and defenseman Larry Murphy are playing for Canada. Defensemen Langway and Kevin Hatcher -- likely playing partners -- and left wing Kelly Miller are on the U.S. team. Wingers Gustafsson and Peter Sundstrom team up for Sweden as they did in the world championships. Capitals defenseman Scott Stevens and Philadelphia Flyers center Dave Poulin were the last two cuts from Team Canada last night.